Many electronic devices communicate with each other using wireless local area networks (WLANs), such as those based on a communication protocol that is compatible with an IEEE 802.11 standard (which is sometimes referred to as ‘Wi-Fi’). For example, during Wi-Fi communication, electronic devices access a shared channel using a contention-based channel-access technique.
In order to reduce power consumption while determining channel availability by listening for transmissions on the shared channel, Wi-Fi includes a virtual carrier-sensing technique. In particular, the medium access control (MAC) layer frame header transmitted by a first electronic device usually contains a duration field (which is referred to as a NAV) that specifies a transmission-time duration required for the frame. During the transmission-time duration specified by the NAV the shared channel is expected to be busy. Using the NAV, another electronic device in a WLAN may set a count-down value in a counter. The other electronic device may use the value in the counter as an indication for how long it should defer from accessing the shared channel and, thus, how long it does not need to listening for transmissions on the shared channel.
However, the virtual carrier sensing provided by the NAV is typically coarse and involves the electronic devices estimating the transmission-time duration. There are often changes in data traffic and/or the transmission-time duration may be less than the amount of time specified by the NAV. When this occurs, an electronic device in the WLAN may transmit an additional CF-End frame to alert other electronic devices in the WLAN that the shared channel is no longer busy (i.e., to free up the remaining time previously specified by the NAV). In response, the other electronic devices in the WLAN may also transmit a CF-End frame. These transmissions constitute additional overhead in the WLAN and can increase the power consumption of the electronic devices, which can reduce their battery life.